Blame the right Windows header for these insane defines.

Everyone is fired.
Use non-default initial clear color in Renderer.

Set it to some non-trivial value to achieve these two things:

 * Some "corporate identity", I find very dark gray nicer than pure
   black.
 * Easier "black screen" debugging. Native Client, for example, by
   default clears to pure white, which caused me painful hours figuring
   out what the hell is going on.
Merge branch 'master' into compatibility
Removed enum-referencing Doxygen workarounds.

In 1.8.5 it is now possible to reference directly to enum member.
Hooray! Also added explicit @ref here and there, fixing some referencing
bugs along the way.
Removed Doxygen workarounds for forward declarations.
Removed annoying Doxygen workaround for #undef.
TextureTools: added `magnum-distancefield` utility.

Standalone command-line executable allowing for easy conversion of
black&white images to distance field texture.
Proper noexcept move constructor for Mesh.

Also documented the inability to copy.
Noexcept moving for Buffer, documented inability to copy.
Primitives: added texture coordinates to Plane and Square primitives.
Assert that the file is really closed after closing it in importer.

Should harden plugin implementations a bit more.
Properly use C++11 enums everywhere.
Adapted to Corrade changes.
MeshTools: added fullScreenTriangle() utility function.

I got bored of copy/pasting and redocumenting/redebugging this code in
every full screen effect ever implemented.
Use `sdl2` dependency in ArchLinux development package.
Merge branch 'master' into compatibility

Conflicts:
	src/Primitives/Plane.cpp
	src/Primitives/Square.cpp
	src/SceneGraph/SceneGraph.h
Trade: something got f'ed up in 9d0c6b44de474f6afaaf4df88908e5b5a35e54bd.
GCC 4.4 compatibility: some explicit typing needed.